Background: Microbiota in the gut is known to play a pivotal role in host physiology by interacting with the immune and neuroendocrine systems in gastrointestinal tissues.Glucagon-like peptide 1 (GLP-1),a gut hormone,is involved in metabolism as well as gastrointestinal motility.We examined how gut microbiota affects the link between GLP-1/GLP-1 receptor (GLP-1R) expression and motility of the gastrointestinal tract.Methods: Germ-free (GF) mice (6 weeks old) were orally administered a fecal bacterial suspension prepared from specific pathogen-free mice,and then after fecal transplantation (FT) gastrointestinal tissues were obtained from the GF mice at various time points.The expression of GLP-1 and its receptor was examined by immunohistochemistry,and gastrointestinal transit time (GITT) was measured by administration of carmine red solution.Results: GLP-1 was expressed in endocrine cells in the colonic mucosa,and GLP-1R was expressed in myenteric neural cells throughout the gastrointestinal wall.GLP-1R-positive cells throughout the gastrointestinal wall were significantly fewer in GF mice with FT than in GF mice without gut microbiota reconstitution.The GITT was significantly shorter in GF mice with FT than in control GF mice without FT,and tended to be correlated with the number of GLP-1R-positive cells throughout the gastrointestinal wall.Conclusions: Gut microbiota may accelerate or at least modify gastrointestinal motility while suppressing GLP-1R expression in myenteric neural cells throughout the gastrointestinal tract.